pod install を実行した際に、↓こんな風にエラーが出てしまいました

[!] Pod::Executable pull

A   AFHARchiver/0.2.1/AFHARchiver.podspec

A   AFWunderlist/1.0/AFWunderlist.podspec

(省略)

A   ym/1.2.6/ym.podspec

A   zipzap/6.0/zipzap.podspec
Pull is not possible because you have unmerged files.

Please, fix them up in the work tree, and then use 'git add/rm <file>'

as appropriate to mark resolution, or use 'git commit -a'.

原因

2014/1/30にSpecsのリポジトリが壊れてしまったようです。

Repairing Our Broken Specs Repository http://blog.cocoapods.org/Repairing-Our-Broken-Specs-Repository/

Unfortunately we've encountered a bug in libgit2 and we are going to have to force push into the Specs repository. (Also known as the ‘master’ spec repo.)

What does this mean for you?
Well, basically your CocoaPods setup is going to break.

You are going to have to manually delete any local copies of the Specs repository and re-clone the new version of the Specs repository.

You can do that with the following commands:

pod repo remove master
pod setup

解決策

セットアップが完了するまで数分かかりました。

pod repo remove master
pod setup

参考

Error on pod install - stack overflow http://stackoverflow.com/questions/18224627/error-on-pod-install